One of the methods for making hardboard panels, consists in digesting sawdust and shavings, defibering same through a refiner zone. Then the resulting stock which is highly diluted in water together with other conventional additives is put into contact with a perforated roll to produce a mat which is then squeezed in between press rolls to be finally dried.
Today, hardboard panel is one of the most commonly used materials for making exterior sidings, these compete against vinyl and aluminum sidings. However, hardboard panel is heavy, transportation cost is also higher, as compared against other sidings. This is even more so as energy cost rises.
In order to qualify for exterior sidings, a panel must be rigid, be able to withstand high variation in temperature, various degrees of humidity and high sun intensity. The temperature gradient in siding is very high at times: one side may be near room temperature, while the other side is well below freezing temperature or at 140.degree.-190.degree. F.